The present invention relates to a semiconductor device and is, for example, a technology applicable to a semiconductor device having a diffusion layer embedded into a substrate.
In a semiconductor device, it sometimes happens that a diffusion layer is embedded into a substrate and a transistor is formed over the diffusion layer. In the transistor, a substance formed by epitaxially growing a semiconductor layer over a semiconductor substrate acting as a base is used as the substrate for example. Then the diffusion layer is: formed by an ion implantation method after the semiconductor layer is formed in some cases; or formed when the semiconductor layer is epitaxially grown in other cases.
Meanwhile, Japanese Unexamined Patent Application Publication No. Sho 62 (1987)-40719 describes that p-type impurities are diffused over the surface of a p-type substrate acting as a base by a thermal diffusion method and successively an epitaxial layer is grown over the substrate.
Further, Japanese Unexamined Patent Application Publication No. 2002-176177 describes that a semiconductor substrate is formed by forming an n-type epitaxial layer over the surface of a p-type substrate acting as a base and a trench gate type IGBT is formed by using the semiconductor substrate. In Japanese Unexamined Patent Application Publication No. 2002-176177, the epitaxial layer has a configuration formed by stacking a low-concentration n-type layer over a high-concentration n-type layer.